Re: [Qemu-devel] QEMU/NEMU boot time with several x86 firmwares

[Rob Bradford]

Hi Stefano,

On Mon, 2018-11-26 at 17:40 +0100, Stefano Garzarella wrote:
> Hi Samuel, Rob,
> I'm proceeding to compare several x86 firmwares in order to
> understand
> which suits better with -kernel option to have a fast boot with
> QEMU/NEMU.
> 
> For your use cases, what boot time do you expect?
> 

Kata Containers, one of the use cases we're looking at, is very
sensitive to boot time, although it is configurable, the default
configuration is to use qemu-lite with it's direct to kernel loader.

That is probably a baseline we should be comparing with.

As an aside, yesterday I posted the Seabios patches for enabling on
NEMU/virt:

https://github.com/rbradford/seabios/tree/virt-x86

I didn't yet start optimising the configuration file we use for it
beyond getting it < 128KiB or apply any optimisation patches.

And I also have some qboot patches too:

https://github.com/rbradford/qboot/tree/virt-x86

So we're in a situation where we can start comparing other machine
types against virt too.

> 
> I compared SeaBIOS, qboot, and OVMF. I started each test using this
> qemu parameters: "./qemu-system-x86_64 -bios path/to/bios.bin -m 1G
> -cpu host -M accel=kvm -vga none -kernel path/to/bzImage -initrd
> path/to/rootfs.cpio ..."
> 
> As Samuel suggested, I added the total time to userspace adding a
> probe in the kernel_init(), so the times (in msec) that I measured
> are:
> - qemu_init_end: first kvm_entry (i.e. QEMU initialized has finished)
> - fw_start: first entry of the firmware
> - fw_do_boot: after the firmware initialization (e.g. PCI setup,
> etc.)
> - linux_start_boot: before the jump to the Linux kernel
> - linux_start_user: before starting the init process
> 
> * SeaBIOS
> Default configuration without debug messages (CONFIG_DEBUG_LEVEL=0) +
> Stephen's patch (tpm: Check for TPM related ACPI tables before
> attempting hw) + my patch (qemu: fast boot when linuxboot optionrom
> is
> used).
>  qemu_init_end: 41.634812
>  fw_start: 41.857374 (+0.222562)
>  fw_do_boot: 52.754109 (+10.896735)
>  linux_start_boot: 54.117220 (+1.363111)
>  linux_start_user: 495.684199 (+441.566979)
> 
> * qboot
> Default configuration + my patch (pci: reduce pci_foreach() calls).
>  qemu_init_end: 40.233717
>  fw_start: 40.384048 (+0.150331)
>  fw_do_boot: 45.660497 (+5.276449)
>  linux_start_boot: 47.252119 (+1.591622)
>  linux_start_user: 509.173886 (+461.921767)
> 
> * OVMF (https://github.com/intel/ovmf-virt)
> I followed this script
> (
> https://github.com/intel/nemu/blob/topic/virt-x86/tools/CI/run_nats.sh
> )
> to build OVMF.
> Note: I put the "fw_start" probe in the BdsEntry()
> [MdeModulePkg/Universal/BdsDxe/BdsEntry.c], I'm not sure if it is
> "near" to the real entry point.
>  qemu_init_end: 42.734555
>  fw_start: 163.611506 (+120.876951)
>  fw_do_boot: 369.713760 (+206.102254)
>  linux_start_boot: 370.960364 (+1.246604)
>  linux_start_user: 796.799667 (+425.839303)
> 
> For OVMF case, are reasonable the times that I measured? Do you use a
> different configuration?
> 

That is the same OVMF configuration as we normally use, I have the
configuration file checked in. Those numbers look like the ones I
expect.

> Thanks,
> Stefano
> 

Great work,

Rob